Core Facebook use (including Messenger) fell 10% in aggregated time spent for all content measured.

Even including Instagram and WhatsApp, Pivotal says it still observed a 6% decline.

The bottom line: "While many investors continue to look for Instagram to support longer-term growth for Facebook at a corporate level, we note that Instagram remains relatively small, at only 13% of Facebook’s size (measured by time spent on the platform by all of its users)," Wieser writes.

He also notes that shares of consumption for Snapchat and Twitter remain relatively stability.